Medium: water;900mL.

Apparatus 2: 50rpm.

Time: 30minutes.

Procedure— Determine the amount of C12H20N2O3S·HCl dissolved by employing UVabsorption at the wavelength of maximum absorbance at about 230nm on filtered portions of the solution under test,in comparison with a Standard solution having a known concentration of USP Sotalol Hydrochloride RSin the same Medium.

Tolerances— Not less than 80%(Q)of the labeled amount of C12H20N2O3S·HCl is dissolved in 30minutes.

Phosphate buffer— Dissolve 6.8g of monobasic potassium phosphate in about 800mLof water.Dilute with water to 1000mL,and mix.

Mobile phase— Prepare a filtered and degassed mixture of Phosphate bufferand acetonitrile (9:1).

Internal standard solution— Transfer about 1.8g of caffeine,accurately weighed,to a 1000-mLvolumetric flask.Dissolve in and dilute with water to volume,and mix.

Standard preparation— Transfer about 80mg of USP Sotalol Hydrochloride RS,accurately weighed,to a 25-mLvolumetric flask.Add 2.5mLof 1Nhydrochloric acid,dissolve in and dilute with water to volume,mix,and filter.Transfer 10.0mLof the filtrate and 25.0mLof the Internal standard solutionto a 200-mLvolumetric flask.Dilute with water to volume,and mix.

Assay preparation— Transfer an appropriate number of Tablets,equivalent to about 800mg of sotalol hydrochloride,to a 250-mLvolumetric flask.Add 25mLof 1Nhydrochloric acid,and swirl.Dilute with water to about three-fourths of the volume of the flask,and shake for 15minutes.Dilute with water to volume,mix,and filter.Transfer 10.0mLof this solution and 25.0mLof the Internal standard solutionto a 200-mLvolumetric flask.Dilute with water to volume,and mix.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 238-nm detector and a 3.9-mm ×30-cm column that contains packing L1.The flow rate is about 1.5mLper minute.Chromatograph the Standard preparation,and record the peak areas as directed for Procedure:the relative retention times for sotalol and caffeine are about 1.0and 2.0,respectively;the resolution,R,between caffeine and sotalol is not less than 6.0;and the relative standard deviation for replicate injections,determined from peak area ratios,is not more than 2.0%.

Procedure— Separately inject equal volumes (about 25µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the areas for the major peaks.Calculate the quantity,in mg,of sotalol hydrochloride (C12H20N2O3S·HCl)in the portion of Tablets taken by the formula: in which Cis the concentration,in mg per mL,of USP Sotalol Hydrochloride RSin the Standard preparation;and RUand RSare the peak area ratios of sotalol to caffeine obtained from the Assay preparationand the Standard preparation,respectively.